What is the diagnosis and management for a 59-year-old male with a 3-day history of gassy abdominal pain, constipation, hypertension, and atrial fibrillation, presenting with hypokalemia?

Diagnosis and Management of 59-Year-Old Male with Abdominal Pain, Constipation, and Atrial Fibrillation

Primary Diagnosis

This patient requires immediate evaluation for acute mesenteric ischemia given the constellation of abdominal pain out of proportion to examination findings, atrial fibrillation (high embolic risk), and cardiovascular disease, which represents a surgical emergency until proven otherwise. 1

SOAP Format

Subjective

• Chief Complaint: 3 days of gassy abdominal pain with radiation throughout abdomen, most prominent in right mid-to-lower quadrant 1
• Associated Symptoms:
  • Constipation for 3 days 1
  • No fever, no vomiting 1
• Past Medical History:
  • Hypertension on Losartan and Amlodipine 1
  • Atrial fibrillation (documented on ECG) - critical risk factor for arterial embolism 1, 2
  • Suppressed TSH (<0.1) suggesting hyperthyroidism, which can exacerbate atrial fibrillation 1

Objective

• Vital Signs: Not fully documented but patient appears stable (no fever noted) 1

• Physical Examination Findings:

  • Abdominal pain with gassy distension 1
  • Critical consideration: Pain severity relative to physical findings must be assessed - "pain out of proportion to physical findings" is pathognomonic for mesenteric ischemia 1
  • Must examine for peritoneal signs (rigidity, rebound, guarding) which would indicate bowel infarction requiring immediate surgery 1

• Laboratory Results:

  • Hyponatremia: Na 131.9 (normal 135-145) 1
  • Hypokalemia: K 3.45 (low-normal to low) - concerning in context of atrial fibrillation as hypokalemia correlates with increased thrombotic risk 3, 4
  • Chloride: 96.8 (normal) 1
  • TSH <0.1 (suppressed) - indicates hyperthyroidism, a secondary cause of hypertension and atrial fibrillation 1
  • WBC 8.59 (normal) - absence of leukocytosis does NOT exclude mesenteric ischemia 1
  • Hemoglobin 14.4, Hematocrit 0.44 (normal) 1
  • Neutrophils 0.58 (normal), Lymphocytes 0.18 (low), Monocytes high, Eosinophils 0.09 1
  • Platelets 173 (normal) 1

• ECG: Atrial fibrillation with controlled ventricular response 1

Assessment

Primary Differential Diagnoses (in order of urgency):

1. Acute Mesenteric Ischemia (Arterial Embolism) - HIGHEST PRIORITY

   • Atrial fibrillation is present in approximately two-thirds of patients with acute mesenteric arterial embolism 1, 2
   • Classic presentation: abdominal pain out of proportion to physical findings in patient with cardiovascular disease 1
   • Mortality approaches 60% if diagnosis delayed 1
   • Absence of fever and normal WBC do not exclude this diagnosis 1

2. Acute Mesenteric Ischemia (Non-occlusive)

   • Can occur in setting of atrial fibrillation with low cardiac output 1
   • Hypokalemia may contribute to cardiac dysfunction 3

3. Diverticulitis

   • Right-sided or sigmoid diverticulitis possible given age >40, constipation, and localized right lower quadrant pain 5
   • However, absence of fever and normal WBC make this less likely 5

4. Constipation/Fecal Impaction

   • 3-day history of constipation with gassy abdomen 1
   • Can cause significant abdominal pain and distension 1
   • However, must rule out mechanical obstruction or ischemia first 1

5. Small Bowel Obstruction

   • Constipation and abdominal pain could indicate obstruction 1
   • Absence of vomiting makes complete obstruction less likely 1

Plan

IMMEDIATE ACTIONS (within 1 hour):

1. Imaging - CT Angiography (CTA) of Abdomen/Pelvis with IV Contrast

   • Triple-phase CT (non-contrast, arterial, portal venous phases) is the diagnostic test of choice 1
   • Evaluates for:
     • Arterial occlusion (embolus vs. thrombosis) in celiac, SMA, or IMA 1
     • Bowel wall changes (thickening, pneumatosis, portal venous gas) 1
     • Free air indicating perforation 1
     • Alternative diagnoses (diverticulitis, obstruction) 1
   • Do NOT perform duplex ultrasound - contraindicated in acute setting due to time delay and poor sensitivity with bowel gas/distension 1

2. Surgical Consultation - STAT

   • Any patient with suspected acute mesenteric ischemia requires immediate surgical evaluation 1
   • If peritoneal signs present → immediate surgical exploration 1
   • If no peritoneal signs but high suspicion → prepare for possible endovascular or surgical intervention 1

3. Laboratory Studies

   • Lactate level - elevated in bowel ischemia but normal lactate does not exclude diagnosis 1
   • Complete metabolic panel - already partially done 1
   • Correct hypokalemia to >4.0 mEq/L given atrial fibrillation and increased thrombotic risk 3, 4
   • Stool occult blood - may be positive in ischemia 1

4. Supportive Care

   • NPO (nothing by mouth) 1
   • IV fluid resuscitation with normal saline 1
   • Nasogastric tube if vomiting develops or bowel obstruction suspected 1
   • Correct electrolyte abnormalities (potassium, sodium) 3

DEFINITIVE MANAGEMENT (based on CTA results):

If CTA shows SMA embolus WITHOUT peritoneal signs or bowel infarction:

• Systemic anticoagulation with heparin (if not contraindicated) 1
• Endovascular intervention preferred as first-line:
  • Angiography with aspiration embolectomy 1
  • Consider transcatheter thrombolysis 1, 6
  • Technical success rates up to 94% with lower morbidity than surgery 1
• Note: Up to 70% may still require surgical bowel resection 1

If CTA shows bowel infarction (pneumatosis, portal venous gas, free air) OR peritoneal signs present:

• Immediate surgical revascularization and bowel resection 1
• This is a surgical emergency - do not delay for endovascular attempts 1

If CTA shows non-occlusive mesenteric ischemia (patent vessels with bowel changes):

• Angiography with infusion of vasodilator (papaverine) into SMA 1
• Optimize cardiac output and blood pressure 1
• Correct hypokalemia to improve cardiac function 3

If CTA shows alternative diagnosis (diverticulitis, obstruction, etc.):

• Manage according to specific diagnosis 1, 5

SECONDARY MANAGEMENT ISSUES:

1. Atrial Fibrillation Management

   • Patient requires long-term anticoagulation to prevent recurrent embolic events 1
   • Once acute ischemia excluded or treated, initiate oral anticoagulation (warfarin or DOAC) 1
   • Ensure rate control is adequate 1

2. Hyperthyroidism Evaluation

   • TSH <0.1 requires endocrinology consultation 1
   • Hyperthyroidism is a secondary cause of atrial fibrillation and hypertension 1
   • Check free T4, free T3 1
   • May require antithyroid medication 1

3. Hypokalemia Correction

   • Target potassium >4.0 mEq/L in patient with atrial fibrillation 3, 4
   • Oral potassium supplementation if able to take PO, otherwise IV potassium 3
   • Hypokalemia inversely correlates with D-dimer and thrombotic risk in atrial fibrillation 4

4. Hypertension Management

   • Continue home antihypertensives (Losartan, Amlodipine) if hemodynamically stable 1
   • Monitor blood pressure closely during acute illness 1

If Constipation is Primary Problem (after excluding ischemia/obstruction):

• Digital rectal examination to assess for fecal impaction 1
• Suppositories or enemas for impaction 1
• Conventional laxatives as first-line for opioid-induced or functional constipation 1
• Consider prucalopride if refractory 1

Critical Pitfalls to Avoid

• Never dismiss abdominal pain in a patient with atrial fibrillation as "just constipation" - mesenteric embolism must be excluded first 1, 2
• Normal WBC and absence of fever do NOT exclude mesenteric ischemia 1
• Do not delay imaging or surgical consultation - mortality increases dramatically with delayed diagnosis 1
• Do not perform duplex ultrasound in suspected acute mesenteric ischemia - it is contraindicated and wastes critical time 1
• Do not start laxatives or enemas until mechanical obstruction and ischemia are excluded 1
• Hypokalemia in atrial fibrillation increases thrombotic risk - must be corrected 3, 4